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It's beyond dispute that Donald Trump has the momentum in the presidential race.

It's also beyond dispute that he still has an incredibly narrow path to get to 270 electoral votes and the presidency.

Let's start with the two most important numbers in this election: 18 and 13.

Eighteen is the number of states every Democratic presidential nominee has carried in each of the past six presidential elections, dating to 1992. Add in the District of Columbia, which also fits the bill, and you get 242 electoral votes.

Thirteen is the number of states every Republican presidential nominee has won in those same presidential elections. Add them up and you get 102 electoral votes.

You don't have to be a Fields Medal winner to quickly grasp Republicans' problem: Their party starts in a significant Electoral College hole, fuelled by several states with large populations - California, New York and Illinois, to name three - that are among the most reliably Democratic in the country.

That problem existed before Trump was even a glint in the eye of Republican voters. And, it's likely to exist well beyond whatever happens to Trump on November 8. But what it means in practical terms is that even as the race has tightened at both the national and swing-state level, Clinton retains far more paths to 270 electoral votes.

Consider this: If Clinton wins the 18 states plus Washington every Democrat has won since 1992 and wins Florida (and its 29 electoral votes), she is president.

There are lots and lots of other ways for Clinton to 270 or beyond. But what's more instructive is to look at the paucity of routes Trump has to reach that same magic number.

Start with an assumption that Trump wins every state that Mitt Romney did in 2012. (That's a bit of a stretch, given that polling in North Carolina, Arizona, Georgia and Missouri - all Romney states - suggests tight contests.)

If we assume that, Trump starts with 206 electoral votes. He needs at least 64 more.

To understand just how narrow his path is, give him Ohio, Florida, Nevada and Iowa. Under that map, he still loses to Clinton - 273 electoral votes to 265.

Trump, realistically, has only three paths. And, by "realistically," I mean within the realm of conceivable. Yes, of course, Trump could run the table of swing states and win easily. But there's little indication that might happen.

1 Win Pennsylvania. If Trump could turn the Keystone State, which is one of the 18 "Blue Wall" states that have gone Democratic in each of the past six elections, then the map opens up for him. Subtract 20 electoral votes from Clinton's presumed 242 and it forces her to add 49 electoral votes rather than just 29.

2 Win Ohio, Florida, Nevada, Iowa and Colorado/Virginia. Colorado and Virginia have been swing states for, at least, the past two elections and, in Colorado's case, far longer. But Trump's struggles with non-white voters have badly complicated his chances in both. Clinton's campaign and its aligned super PAC ceased advertising in both states a month ago - a sign of their confidence about her prospects. Trump continues to spend in Virginia, suggesting that he sees a chance in the Old Dominion.

3 Win Ohio, Florida, Nevada, Iowa and New Hampshire. That scenario gives Trump 269 electoral votes and Clinton 269 electoral votes. If that came to pass - and it's not impossible by any means! - then the election would be thrown to the House of Representatives, where each state would cast a single vote for president. Such an outcome would invalidate Democrats' Electoral College edge; Idaho would have the same amount of sway to choose the president as would California.

None of those three scenarios is outlandish. But all require Trump to not only consolidate the gains he has made over the past few weeks but also expand those gains. His recent surge has brought him back into contention. It has not vaulted him ahead.

The task before him is the equivalent of threading a very narrow needle with 300 million people (or so) watching. That's possible but far from likely. Still.